9514 1404 393
Answer:
36
Explanation:
Let the digits of the number be represented by t for the tens digit and u for the units digit.
u = 2t . . . . . . . . the units digit is twice the tens digit
2(10t +u) = (10u +t) +9 . . . . . double the number is 9 more than its reverse
Substituting for u, we have ...
2(10t +2t) = 10(2t) +t +9
24t = 21t +9 . . . . . . . . . . . collect terms
3t = 9 . . . . . . . . . . . . . subtract 21t
t = 3 . . . . . . . . . . . divide by 3
u = 2t = 6 . . . . find u
The number is 36.